what is dissolved oxygen measured in

What Is Dissolved Oxygen Measured In?

Oxygen is a crucial element for supporting life in all forms. It is the most essential component that organisms need to breathe and carry out their day-to-day activities. In aquatic ecosystems, dissolved oxygen is an important indication of the water quality, and it has a direct impact on the living conditions of aquatic plants and animals.

Dissolved oxygen levels in water can vary greatly depending on various factors, such as water temperature, pressure, and salinity. In order to maintain the ideal level of dissolved oxygen required for the survival of aquatic life, it is important to have knowledge of how dissolved oxygen is measured.

In this article, we will explore what dissolved oxygen is measured in and some of the commonly used methods for measuring dissolved oxygen levels in water.

What Is Dissolved Oxygen

Dissolved oxygen is the oxygen that is present in water and available for aquatic life to breathe. It is the oxygen that has been absorbed into water from the surrounding atmosphere through diffusion. Oxygen levels in water can range from 0 to 14.6 milligrams per liter (mg/L). Dissolved oxygen is measured in mg/L, ppm (parts per million), or percent saturation.

Factors That Affect Dissolved Oxygen Levels

The level of dissolved oxygen in water can be impacted by a variety of factors. These factors can include physical and chemical factors such as temperature, pressure, and the presence of pollution. Biological factors, including plants and animals, can also impact dissolved oxygen levels.

Temperature: The level of dissolved oxygen in water decreases as water temperature increases. This means that warmer water can hold less oxygen than colder water.

Pressure: Pressure can impact the solubility of gases including oxygen. At higher pressures, more oxygen can be dissolved into water.

Pollution: Pollution can impact the level of dissolved oxygen in water in several ways. For example, excess nutrients can lead to an overgrowth of algae, which can reduce dissolved oxygen levels. Pollution can also lead to lower oxygen levels in water by reducing photosynthesis, which is how aquatic plants produce oxygen.

Biological factors: Aquatic plants and animals also impact dissolved oxygen levels in water. Photosynthesis by aquatic plants generates oxygen, and respiration by aquatic animals consumes oxygen. In addition, the decomposition of organic matter can consume oxygen in water.

Methods for Measuring Dissolved Oxygen Levels

There are several commonly used methods for measuring dissolved oxygen levels in water. These methods include:

1. Winkler Method

The Winkler method is a colorimetric method that measures dissolved oxygen levels through a series of chemical reactions. The method involves adding a series of reagents to a water sample, which ultimately react with dissolved oxygen to create a blue precipitate that can be measured using a spectrophotometer.

2. Membrane Electrode Method

The membrane electrode method uses an electrode that is coated with a gas-permeable membrane. The electrode is placed in a water sample, and the dissolved oxygen that diffuses through the membrane is measured using a meter.

3. Polarographic Method

The polarographic method uses a polarographic electrode that is immersed in a water sample. This electrode creates an electric current that is proportional to the amount of oxygen that is present in the water. The amount of oxygen is then read on a meter.

4. Titration Method

The titration method measures dissolved oxygen levels by titrating a water sample with a chemical solution. The chemical solution reacts with dissolved oxygen to create a color change that can be measured using a titration burette.

5. Optical Method

The optical method uses an optical sensor to measure dissolved oxygen levels in a water sample. The sensor can be placed in a water sample and measure the oxygen content using optical fluorescence or phosphorescence.

Conclusion

Dissolved oxygen is essential for aquatic life, and maintaining a healthy level of dissolved oxygen is critical for the survival of aquatic organisms. Measuring dissolved oxygen levels can be done using several different methods; however, selecting the appropriate method for a specific situation will depend on several factors, such as the required level of accuracy, the availability of equipment, and cost. By understanding the basics of dissolved oxygen and its measurement, we can take steps to promote the health and vitality of aquatic ecosystems.